1. Field of the Invention
This invention relates to power and energy measurement systems and methods, and more particularly to single phase bi-directional power and energy systems and methods which are configured on a single semiconductor chip.
2. Description of the Related Art
Power and energy measurement systems of many kinds are well-known. Many of such systems are electromechanical. Many of these systems are inaccurate and consume excessive power.
There is a need for accurate power and energy measurement systems having enhanced functionality, which are nonetheless inexpensive and which consume reduced energy levels to operate.
According to one embodiment of the present invention, a power and energy measurement system of enhanced accuracy performs a plurality of functions including energy and power measurement, root mean square voltage and root means square current determination, and energy to pulse-rate conversion. The measurement system has reduced power consumption and has an interface which is optimized for operation with a shunt sensor. The measurement system includes a phase compensation system and operates with ground-referenced signals and a single power supply. The system further has a calibration system, including a feature for providing a settable offset useful for determining power level calculations. Further, according to one embodiment of the present invention, the single phase bidirectional power energy system provides an energy data accuracy of 0.1% of reading in one second over 300:1 dynamic range. The system provides a tool to measure and calculate eneregy, power and root mean square current and voltage, while providing a reduced level of power consumption. Further, an interface is optimized for inclusion of a shunt sensor, enabling a low input range and use of a small value resistor, enabling use of a simplified voltage regulator. Further, useful system calibration features according to the present invention, allow an offset to be used for voltage and current calculations. According to one embodiment of the present invention, a monolithic CMOS power measurement device includes an energy computation engine. The device includes a programmable gain amplifier, two delta sigma modulators, two high rate filters, a system calibrator, a power calculator with functions to compute energy, rms voltage, rms current, and instantaneous power. The device performs power meter functions while interfaced to shunt current transformers for current measurement and a voltage transformer or resistive divider to measure voltage. The device includes a programmable gain amplifier in the current channel to accommodate various input voltage levels due to shunts, permitting measurements of 150 or 300 mV rms. The device includes first and second high rate digital filters which output data at a (MCLK/K)/1024 output word rate. A high pass filter in each channel is used to remove DC content prior to energy calculation. The device is further adapted according to the present invention to interface effectively with a microprocessor, controller, or microcontroller over a three wire serial interface which is SPI-compatible and microwire-compatible. The device further includes a serial port which includes a Schmitt Trigger input on its serial clock to accommodate slow rise time signals.